With advancements in microcellular foaming technology and a growing need for lightweight materials having a higher strength-to-weight ratio, various thermoplastic polymer foams have been produced with polystyrene, poly (lactic acid), poly (ethylene terephthalate) and polycarbonate. Amongst the various polymers, polystyrene continues to dominate the thermoplastic foam market today.
Although a linear polypropylene (PP) foam is able to withstand higher service temperatures, usage of this type of foam has been largely restricted by the relatively poor rheological properties of linear polypropylene. Attempts to improve these properties by cross-linking a portion of the linear polymer or by adding a long chained branched polymer have resulted in unwanted side effects, including a reduction in recyclability.